Regardless of whether you file or not, other people will. This then does effect you because either the pump price will increase to cover these costs or you will be taxed more, depending on who pays out and whether the government will contribute to BP. Even if you choose to buy your fuel from another supplier, their insurance etc will now have risen, thereby making them pass the costs on to you at the pump. You are in the fortunate position to be able to claim this back. Despite being in England, I will also be paying for this, but do not have this option. So indirectly you are only protecting against losses to yourself, induced by this accident and should feel no remorse in claiming.
You will probably get more than you would have lost at the pump back, but the anguish this has put you under in itself deserves compensation. Maybe a new car would help ease your troubled mind and hence justice will been done.
You didn't cause this spill. They did. You are the victim now. Don't let them use 'twisted morality' to try to cheat you out of what you deserve.